JP2012171985A - Copolyester and biaxially oriented film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copolyester that has crystallinity and excellent melt heat stability and includes 1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate as a main repeating unit, and a biaxially oriented film using the copolyester.SOLUTION: The copolyester is poly(1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate) obtained by copolymerizing a terephthalic acid component, has a melting point in the range of 270-300°C, and contains a reaction product (A) of a specific phosphonic acid and a metal compound. The biaxially oriented film uses the copolyester.

Description

  The present invention relates to poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate copolymerized with a terephthalic acid component and a film using the same.

  Poly 1,4-cyclohexanedimethylene-1,4-terephthalate is an engineering plastic because it has excellent mechanical properties, electrical properties, other physical and chemical properties, especially heat resistance, and good processability. It is used for various purposes. In particular, since it has excellent heat resistance, it has been used for film applications that require solder heat resistance, but its melt heat stability is insufficient. Therefore, with respect to poly 1,4-cyclohexanedimethylene-1,4-terephthalate, a method of using a combination of polymerization catalysts (Patent Document 1: Japanese Patent Laid-Open No. 2002-338664) or polymerization by adding a polymerization catalyst until now. A technique for improving the speed (Patent Document 2: Japanese Patent Laid-Open No. 2000-178349) and a technique for copolymerizing a specific glycol component (Patent Document 3: Japanese Patent Laid-Open No. 4-261423) have been studied. However, even with these methods, it has been difficult to provide sufficient melting heat stability.

  By the way, poly 1,4-cyclohexane dimethylene-2,6-naphthalene dicarboxylate using 2,6-naphthalenedicarboxylic acid instead of terephthalic acid is disclosed in Patent Document 4 (Japanese Patent Laid-Open No. Hei 1-2201325). Proposed. However, the poly 1,4-cyclohexanedimethylene-2,6-naphthalene dicarboxylate specifically proposed here has a high melting point of 320 ° C. or higher, so that facilities for polymerization and molding are limited. Further, when they were tried to form a film, only those having poor melt heat stability were obtained because they involved melt kneading at a very high temperature.

  In addition, 1,4-cyclohexanedimethylene-2,6-naphthalene dicarboxylate tends to bump easily in the polymerization process, and not only requires the addition of an antifoaming agent during polymerization, There is also a problem of lowering productivity because it is necessary to reduce the amount charged. In addition, because of high reactivity, the melt heat stability also tends to be poor, and the mechanical strength of the molded product tends to decrease.

JP 2002-338664 A JP 2000-178349 A JP-A-4-261423 JP-A-1-201325

  An object of the present invention is to use a copolyester having 1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate as a main repeating unit, which has crystallinity and is excellent in melt heat stability, and the same. It is to provide a biaxially oriented film.

  Accordingly, the present inventor has studied the copolymerization of 1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate in an attempt to solve the above-mentioned problems. It was found that by making the content in a specific range, bumping at the time of polymerization can be suppressed while maintaining the heat stability of melting superior to 1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate. On the other hand, since the crystallinity of the polymer is greatly reduced by copolymerization of the acid component, it has been found that film formation becomes difficult as a result. As a result of further research, it was found that the crystallinity can be maintained by adding specific reactants, and the polymer crystallinity, heat resistance, heat stability of melting, and process stability during polymerization were also provided. The inventors have found that a copolyester can be obtained and have reached the present invention.

（上記式中のＲ^６は、炭素数１〜１２個の炭化水素基であるアルキル基、アリール基またはベンジル基を表し、Ｒ^７、Ｒ^８は、それぞれ独立に水素原子または炭素数の１〜１２個の炭化水素基であるアルキル基、アリール基またはベンジル基を表す。）
（ロ）テレフタル酸成分の共重合量が、全酸成分のモル数を基準として、５〜２５モル％の範囲にある上記（イ）記載の共重合ポリエステル。
（ハ）金属化合物が、マンガン、亜鉛、マグネシウムおよびカルシウムからなる群より選ばれる少なくとも１種の金属化合物である上記（イ）記載の共重合ポリエステル。
（ニ）リン化合物がフェニルホスホン酸である上記（イ）または（ロ）記載の共重合ポリエステル。
（ホ）共重合ポリエステルの重量を基準としたとき、上記反応物（Ａ）に由来する金属元素量とリン元素量とが、それぞれ５０〜１５０ｐｐｍと２５〜１００ｐｐｍの範囲である上記（イ）または（ロ）記載の共重合ポリエステル。
（ヘ）上記（イ）、（ロ）または（ハ）記載の共重合ポリエステルからなる二軸配向フィルム。 Thus, according to the present invention, a copolyester satisfying the following (a) to (e) and a biaxially oriented film of the following (f) comprising the same are provided.
(A) Poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate copolymerized with a terephthalic acid component, the melting point being in the range of 270 to 300 ° C., and the following formula (A) Copolyester containing the reaction product (A) of the phosphorus compound and metal compound which are represented.

(R ⁶ in the above formula represents an alkyl group, aryl group or benzyl group which is a hydrocarbon group having 1 to 12 carbon atoms, and R ⁷ and R ⁸ are each independently a hydrogen atom or 1 to 1 carbon atoms. Represents an alkyl group, aryl group or benzyl group which is 12 hydrocarbon groups.)
(B) The copolymerized polyester according to (a) above, wherein the copolymerization amount of the terephthalic acid component is in the range of 5 to 25 mol% based on the number of moles of all acid components.
(C) The copolyester according to (a) above, wherein the metal compound is at least one metal compound selected from the group consisting of manganese, zinc, magnesium and calcium.
(D) The copolyester according to (a) or (b) above, wherein the phosphorus compound is phenylphosphonic acid.
(E) When based on the weight of the copolyester, the amount of the metal element and the amount of phosphorus element derived from the reaction product (A) are in the range of 50 to 150 ppm and 25 to 100 ppm, respectively, (B) Copolyester as described.
(F) A biaxially oriented film comprising the copolymerized polyester described in (a), (b) or (c) above.

  ADVANTAGE OF THE INVENTION According to this invention, the copolyester which can suppress bumping at the time of superposing | polymerizing 1, 4- cyclohexane dimethylene-2, 6- naphthalene dicarboxylate, maintains crystallinity, and has high melt heat stability, and its A film is provided. According to the present invention, it is possible to efficiently produce a biaxially oriented film having good productivity and excellent solder heat resistance.

  The copolymerized polyester of the present invention is poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate copolymerized with terephthalic acid, has a melting point in the range of 270 to 300 ° C., and the above A reaction product (A) of a phosphorus compound represented by the formula (A) and a metal compound is contained.

  The lower limit of the melting point of the preferred copolyester is 275 ° C. or higher, more preferably 280 ° C. or higher, while the upper limit is 295 ° C. or lower, further 290 ° C. or lower. When the melting point is below the lower limit, the film is required to have soldering heat resistance, and the heat resistance is poor. On the other hand, when the melting point exceeds the upper limit, restrictions on the equipment for polymerization and molding are increased.

  In the present invention, the copolymerization component for poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate is terephthalic acid. Ethylene glycol or the like does not exhibit a sufficient effect in suppressing bumping. The copolymerization amount of the terephthalic acid component is in the range of 5 to 25 mol%, preferably 7 to 22 mol%, more preferably 10 to 20 mol%, based on the number of moles of all acid components. In addition, the total acid component in the present invention means the total number of moles of acid components such as 2,6-naphthalenedicarboxylic acid and terephthalic acid forming the polyester. When this copolymerization amount is less than the lower limit, it becomes easy to bump at the time of the polymerization reaction of the polymer, and it is necessary to reduce the charged amount, so that not only the polymerization process becomes unstable but also the productivity decreases. On the other hand, when the upper limit is exceeded, the melting point is lowered, and the properties such as solder heat resistance of the film are impaired. Of course, the copolymer polyester of the present invention may be copolymerized with a copolymer component known per se, such as an isophthalic acid component and an ethylene glycol component, as long as the effects of the present invention are not impaired.

  The copolymerized polyester of the present invention contains a specific reactant (A) as described above, and this reactant A functions to promote crystallization of the polymer by forming submicron-order particles in the polymer. It is believed that there is. Therefore, if the above-mentioned reactant (A) is not present, the copolyester tends to be amorphous.

  As described above, the reaction product (A) in the present invention is a reaction product of a metallized product and a phosphorus compound represented by the formula (A). The metal compound to be used is not particularly limited, and examples thereof include manganese compounds, zinc compounds, magnesium compounds, calcium compounds, cobalt compounds, and cerium compounds. Among these, manganese compounds, zinc compounds, magnesium compounds, calcium compounds, and the like are preferable. These metal compounds are particularly preferably hydroxides, acetates and carbonates. Among these, manganese or zinc acetate is most preferable. It is estimated that the reaction product of these metal compounds and the following phosphorus compounds improves the crystallinity of the copolymerized polyester and facilitates the formation of a biaxially oriented film.

  Next, the phosphorus compound used to form the reactant (A) is the one represented by the above formula (A), such as phenylphosphonic acid, methyl phenylphosphonate, dimethyl phenylphosphonate, ethyl phenylphosphonate. , Diethyl phenylphosphonate, (2-hydroxyethyl) phenylphosphonate, bis (2-hydroxyethyl) phenylphosphonate, benzylphosphonic acid, methyl benzylphosphonate, dimethyl benzylphosphonate, ethyl benzylphosphonate, diethyl benzylphosphonate, -Naphthylphosphonic acid, 1-naphthylphosphonic acid methyl, 1-naphthylphosphonic acid dimethyl, 1-naphthylphosphonic acid ethyl, 2-naphthylphosphonic acid, 2-naphthylphosphonic acid methyl, 2-naphthylphosphonic acid ethyl, 2-naphthylphosphonic acid Diethyl fonate, diethyl 1-naphthylphosphonate, 4-hydroxybenzylphosphonic acid, methyl 4-hydroxybenzylphosphonate, dimethyl 4-hydroxybenzylphosphonate, ethyl 4-hydroxybenzylphosphonate, diethyl 4-hydroxybenzylphosphonate, Examples include 4-biphenylphosphonic acid, methyl 4-biphenylphosphonate, dimethyl 4-biphenylphosphonate, dimethyl 4-methylbenzylphosphonate, ethyl 4-biphenylphosphonate, diethyl 4-methylbenzylphosphonate. Of these, phenylphosphonic acid is particularly preferable.

  In addition, the reactant (A) in the present invention may be added to the copolyester after reacting the metal compound and the phosphorus compound in advance, or may be reacted during the polymerization reaction of the copolyester. In the case of reacting in advance, for example, a metal compound and a phosphorus compound are used at a molar ratio of each metal element and phosphorus element of 1: 1 to 1: 2, and 100 to 190 ° C. in ethylene glycol. It is easily obtained by heating to temperature. In addition, since the metal compound and the unreacted phosphorus compound are scattered during the polycondensation reaction of the polyester, the molar ratio of the amount of metal element and the amount of phosphorus element is the amount of metal element and the amount of phosphorus element described later. Adjust it.

  In the present invention, the metal element amount and phosphorus element amount derived from the reaction product (A) are preferably in the range of 50 to 150 ppm and in the range of 25 to 100 ppm, respectively, based on the mass of the copolyester. It is preferably in the range of 60 to 135 ppm and 30 to 80 ppm, more preferably in the range of 65 to 110 ppm and 35 to 70 ppm. When these metal element amounts and phosphorus element amounts are less than the lower limit, the crystallinity is lost, making it difficult to produce a biaxially oriented film using the copolymerized polyester of the present invention. On the other hand, if the content exceeds the upper limit, the physical properties of the resulting film may be reduced due to a decrease in the melt heat stability of the copolyester due to the presence of a large amount of the metal compound, or by the cleavage of the molecular chain accompanying the molding process. Is damaged.

  The copolyester of the present invention may be made into a composition by adding a lubricant known per se, for example, inert particles, from the viewpoint of running property and winding property when forming into a film. In addition, other thermoplastic polymers, stabilizers such as UV absorbers, antioxidants, plasticizers, flame retardants, mold release agents, pigments, nucleating agents, fillers or glass fibers, as long as the effects of the present invention are not impaired. Carbon fiber, layered silicate, etc. may be blended as necessary to form a composition. Other thermoplastic polymers include liquid crystalline resins, aliphatic polyester resins, polyamide resins, polycarbonates, ABS resins, polymethyl methacrylate, polyamide elastomers, polyester elastomers, polyether imides, polyimides, and the like. In particular, as a resin to be blended, polyetherimide, liquid crystal resin, and the like are preferable because the heat resistance and the like of the obtained film are easily improved.

  The biaxially oriented film of the present invention is obtained by stretching the above-described copolymer polyester in the film forming direction and the width direction. The laminated structure is not particularly limited, and may be a single layer film or a laminated film having two or more layers. In the case of a laminated film, at least one layer may be the biaxially oriented film of the present invention. In addition, the biaxially oriented film of the present invention is made of the above-mentioned polyester resin, and may contain a known resin or a functional agent as long as the effects of the present invention are not impaired.

Hereinafter, preferred embodiments of the biaxially oriented film of the present invention will be described.
The biaxially oriented film of the present invention is obtained by mixing copolymer polyester pellets with other resin pellets at a predetermined ratio if necessary, and then drying, for example, from an extruder at a melting temperature of 260 ° C to 310 ° C. Extruded into a film through a T die, cast on a cooling drum and cooled and solidified to produce an unstretched film. This unstretched film is stretched in the machine direction at a temperature of 60 to 150 ° C. at a magnification of 3 to 8 times, and then stretched in the transverse direction at a temperature of 70 to 180 ° C. at a magnification of 3 to 7 times to produce a biaxially oriented polyester. A film can be obtained. If necessary, longitudinal and / or transverse stretching may be divided into two or more stages (longitudinal multi-stage stretching, longitudinal-horizontal-vertical three-stage stretching, longitudinal-horizontal-vertical-horizontal 4). Step stretching, etc.). Moreover, you may implement by simultaneous biaxial stretching. The total draw ratio in producing the biaxially oriented film is preferably 10 to 35 times, more preferably 12 to 30 times as the area draw ratio. The biaxially oriented film is preferably heat-set at a temperature of 140 to 265 ° C after biaxial stretching, and particularly preferably heat-set at 180 to 230 ° C. The heat setting time is preferably 1 to 60 seconds.

  When the biaxially oriented polyester film of the present invention is a laminated film, for example, two extruders are used, and at least one of the polyester polyester pellets is sent and melted to form a laminated film from a two-layer or multilayer die. The laminated unstretched film is extruded, and the laminated unstretched film may be subjected to the same stretching and heat treatment as in the case of the single-layer polyester film.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the present invention, the characteristics were measured and evaluated by the following methods.

(1) Intrinsic viscosity Using a mixed solvent of 1,1,2,2-tetrachloroethane (phenol: 1,1,2,2-tetrachloroethane = 40 wt%: 60 wt%) as a solvent, Measurement was performed using an Ostwald viscometer under constant temperature.

(2) Composition of acid component / glycol component of poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate The obtained copolymer polyester was used as a solvent (deuterated trifluoroacetic acid: deuterated chloroform = 50% by weight: dissolved in 50 ^wt.%), by 1 H-NMR [JEOL JEOL a-90 (90MHz)], the acid component 1,4 dimethyl terephthalate, 2,6-dimethyl naphthalate, as glycol components 1 Protons serving as indices such as 1,4-dichlorohexanedimethanol and ethylene glycol were identified, and the content was measured from the peak intensity.

(3) Measurement of residual element amount The obtained poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate is heated and melted to form a circular disk, and a Rigaku fluorescent X-ray apparatus 3270 type is prepared. The amount of metal element and the amount of phosphorus element contained were measured. Note that the amounts of metal elements and phosphorus elements not derived from the reactant A were calculated by removing from the above amounts.

(4) Measurement of differential scanning calorimeter The differential scanning calorimeter was measured using a Q20 type differential scanning calorimeter manufactured by TA Instruments. The measurement conditions are as follows.
Using a differential scanning calorimeter, a polyester sample was heated to 300 ° C. under a nitrogen flow and heated at 20 ° C./min, held at 300 ° C. for 2 minutes, and melted and rapidly cooled in liquid nitrogen. Solidify (when the melting point of the sample exceeds 300 ° C., it is heated to the melting point of the sample + 25 ° C. and held for 2 minutes).
The obtained polyester is heated at a temperature rising condition of 20 ° C./min until reaching the temperature reached before, held for 2 minutes, then scanned under a temperature decreasing condition of 10 ° C./min, and exothermic and endothermic peaks appearing. Were observed, and the glass transition point (Tg), the temperature-rising crystallization temperature (Tci), the melting point (Tm), and the temperature-falling crystallization temperature (Tcd) were measured.

(5) Impact boiling during polymerization Using a 300 mL three-necked flask, an agent was added so that the total charge of the acid component was 0.5 mol and the total charge of the glycol component was 1.0 mol. The transesterification reaction is performed by adding 0.04 mol% of the hydrate to the acid component. After the transesterification reaction, 0.05 mol% of phenylphosphonic acid is added to the acid component, and 0.03 mol% of trimellitic acid titanium is added to the acid component. Then, immerse the three-necked flask in a 300 ° C. bath and reduce the pressure to 1 KPa at a rate of 10 Kpa / min. When the polymerization reaction proceeds, the reaction product bumps and closes the mouth of the flask. Assuming that no bumping occurs and the mouth of the flask is not closed, “None”.

(6) Film forming property Extruded into a film form from a extruder through a T die at a melting temperature of 300 ° C, cast onto a cooling drum, and cooled and solidified to obtain an unstretched film. This unstretched film is stretched 3.0 times in the longitudinal direction while being heated at 130 ° C., stretched 4.0 times in the lateral direction while being heated at 140 ° C., and then heat-set at 230 ° C. for 30 seconds. In the process, it was observed whether the film could be stably formed. Evaluation was made according to the following criteria.
○: Stable film formation for 1 hour or more ×: Cutting occurs within 1 hour, and stable film formation is not possible

(7) Melting heat stability
The obtained polymer was once pelletized, dried at 140 ° C. for 6 hours, and then stirred at a temperature of 300 ° C. for 30 minutes in a molten state. Then, the polymer was recovered and immediately immersed in ice water. Quenched quickly. Then, the intrinsic viscosity (IV ₀ ) of poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate after the drying treatment and before the melting treatment, and the poly-1,4-cyclohexanedimethylene after the melting treatment. The intrinsic viscosity (IV ₃₀ ) of -2,6-naphthalenedicarboxylate was measured. Then, an intrinsic viscosity difference (ΔIV) is obtained by subtracting the intrinsic viscosity (IV ₃₀ ) after the melting treatment from the intrinsic viscosity (IV ₀ ) after the drying treatment and before the melting treatment. It can be said that the smaller the ΔIV, the better the heat stability of melting. In addition, about the thing whose melting | fusing point exceeds 300 degreeC, since there was a problem by film forming etc., it did not evaluate.

[Example 1]
2,6-dimethyl naphthalate (NDC), 1,4-dimethyl terephthalate (DMT), 1,4-cyclohexanedimethanol (CHDM), ethylene glycol (EG) in molar ratio (NDC: DMT / CHDM: EG = 80: 20/140: 60) Further, manganese acetate tetrahydrate was charged into the transesterification reaction tank so as to be 0.040 mol% with respect to the total acid components, and the temperature was raised to 190 ° C. Thereafter, methanol was removed while raising the temperature to 240 ° C. to complete the transesterification reaction.
Subsequently, phenylphosphonic acid and trimellitic acid titanium were charged at 0.050 mol% and 0.030 mol%, respectively, with respect to the total acid components. In addition, the titanium trimellitic acid was added in the state of a 0.6 weight% ethylene glycol solution. The reaction product thus obtained was transferred to a polymerization reaction tank. While raising the temperature in the polycondensation reaction tank, the pressure is slowly reduced, and finally polycondensation is carried out under a polycondensation temperature of 300 ° C. and a vacuum of 50 Pa to produce terephthalic acid copolymer poly-1,4-cyclohexanedimethylene -2,6-naphthalenedicarboxylate was obtained.
The properties of the resulting terephthalic acid copolymer poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate are shown in Table 1.

[Examples 2 to 9]
The same operation as in Example 1 was performed except that the charged amount was changed so that the composition of NDC, DMT, CHDM, and EG and the amount of remaining elements were as shown in Table 1. However, in Example 9, Irganox 1010 (manufactured by Ciba) was added at 0.5% by mass with respect to the weight of all acid components at the same time as the addition of phenylphosphonic acid.

[Comparative Example 1]
The same operation as in Example 1 was performed except that the charged amount was changed so that the composition of NDC, DMT, CHDM, and EG and the amount of remaining elements were as shown in Table 1. However, the polycondensation temperature was 310 ° C.

[Comparative Examples 2, 3, 5, 6, 8]
The same operation as in Example 1 was performed except that the charged amount was changed so that the composition of NDC, DMT, CHDM, and EG and the amount of remaining elements were as shown in Table 1.

[Comparative Example 4]
The same operation as in Example 1 was performed except that the charged amount was changed so that the composition of NDC, DMT, CHDM, and EG and the amount of remaining elements were as shown in Table 1. However, the polycondensation reaction was performed such that the total charge was 70% by weight with respect to Example 1 in order to avoid bumping during polymerization.

[Comparative Example 7]
The same operation as in Example 1 was performed except that the charged amount was changed so that the composition of NDC, DMT, CHDM, and EG and the amount of remaining elements were as shown in Table 1. However, trimethyl phosphate (structural formula B) was used as the phosphorus compound instead of phenylphosphonic acid.

[Comparative Example 9]
The same operation as in Example 1 was performed except that the charged amount was changed so that the composition of NDC, DMT, CHDM, and EG and the amount of remaining elements were as shown in Table 1. However, the polycondensation temperature was 330 ° C., and the reaction was carried out so that the total charge was 70% by weight with respect to Example 1 in order to avoid bumping during polymerization.

  In Table 1, NDC is 2,6-dimethylnaphthalate component, DMT is 1,4-dimethylterephthalate component, CHDM is 1,4-cyclohexanedimethanol component, EG is ethylene glycol component, Irg1010 is Irganox 1010 (manufactured by Ciba) ), Tg means glass transition point (° C.), Tci means temperature rising crystallization temperature (° C.), Tm means melting point (° C.), and Tcd means temperature falling crystallization temperature (° C.).

  The biaxially oriented polyester film of the present invention can be used for various applications such as magnetic recording, industrial materials, packaging, agriculture, and building materials, and is particularly suitable as a film for applications requiring solder heat resistance. Can be used.

Claims (6)

Poly-1,4-cyclohexanedimethylene-2,6-naphthalenedicarboxylate copolymerized with a terephthalic acid component, having a melting point in the range of 270 to 300 ° C. and represented by the following formula (A) A copolyester containing a reaction product (A) of a phosphorus compound and a metal compound.

(R ⁶ in the above formula represents an alkyl group, aryl group or benzyl group which is a hydrocarbon group having 1 to 12 carbon atoms, and R ⁷ and R ⁸ are each independently a hydrogen atom or 1 to 1 carbon atoms. Represents an alkyl group, aryl group or benzyl group which is 12 hydrocarbon groups.)   The copolymerized polyester according to claim 1, wherein the copolymerization amount of the terephthalic acid component is in the range of 5 to 25 mol% based on the number of moles of all acid components.   The copolymer polyester according to claim 1, wherein the metal compound is at least one metal compound selected from the group consisting of manganese, zinc, magnesium and calcium.   The copolyester according to claim 1 or 2, wherein the phosphorus compound is phenylphosphonic acid.   The metal element amount and phosphorus element amount derived from the reactant (A) are in the range of 50 to 150 ppm and 25 to 100 ppm, respectively, based on the weight of the copolyester. Copolyester.   A biaxially oriented film comprising the copolymerized polyester according to any one of claims 1 to 5.